Visual acuity is typically measured with a functional test of the most central part in the visual system, and relates to the function of fovea of the retina and the nerve and brain function related to this area. Many early diseases of the visual system do not change the visual acuity, but rather change the function in smaller or larger areas of the visual field or change the binocular vision. There is often a significant discrepancy between objective tests, visual acuity and function in the visual field.
The most common eye diseases affecting the central visual field are Age Related Maculopathy, Diabetic Retinopathy and Glaucoma. To discover and to follow treatment of these eye diseases are utmost important.
Among doctors, ophthalmologists, opticians and other individuals who perform examinations of visual functions, there is an unmet need with respect to the ability of examining clinically relevant visual functions in the central visual field and binocular vision by means of simple methods. In addition, there is a need for self-examination among people who have an increased risk of diseases in retina, visual pathways and brain, and among patients who have previously had diagnosed such diseases and are at risk of progression. If these patients themselves have the possibility of discovering early pathological, functional changes in the visual system, or discovering important clinical changes detected previously, prevention or treatment may be initiated quicker and with better results.
Visual functions that may advantageously be examined comprise:                the visual field from 0 to 10 degrees        the visual field from 10 to 25 degrees        Binocular visual functions.        
The central part of the visual field within a distance of 10 degrees from the center corresponds to most of the macular area in the central part of the retina of the eye. Some visual functions in this area may be affected in different ways by diseases in the macular area of the retina (maculopathy) or by changes in front of or below this area of the retina. These diseases may involve small defects (scotomas) in the visual field (FIG. 1), because sensory cells, nerve cells or nerve threads in this area have ceased or depressed function. In addition, changes in the microstructure of the retina or other impact on the sensory cells of the retina may occur. This may result in metamorphopsia (FIG. 2), where straight lines are seen as broken, bent, wavy, vibrating, twisted or colored lines. Metamorphopsia is a typical symptom, which can often be related to functional disturbances in the retina. The visual perception of scotomas and metamorphopsia is modulated by dynamic changes in the plasticity of the brain.
Some of the causes of functional changes in the macular area in the form of scotomas and metamorphopsia may be membranes or obscurities in front of parts of the macula. Holes in the retina, oedema, bleeding, inflammation, toxic impact, tumor formation or membrane formation and in-growth of new blood vessels (neovascularization) in the macula or just below the macula (subretinal neovascular membranes) may be other causes.
Pathological visual functions in the visual field from 10 to 25 degrees may be caused by glaucoma, diseases in the retina, visual nerves, and visual pathways and in the brain. Pathological binocular functions may occur, if the visual development does not proceed normally, after traumas, pathological changes in eyes and eye surroundings, chemical impacts, or diseases which affect the normal control and regulation of the binocular vision.
Known Examination Systems
With various forms of visual field examination (perimetry), it is possible to examine various parts of the visual field. To this end, computer-controlled, high-technological instruments (automatic perimetry), which lend themselves to stationary use, are frequently employed. Functional impairment or functional cessation in some areas of the visual field may be detected with these instruments. But, it is not possible to detect the special changes in the form of metamorphopsia (FIG. 2) in this manner.
Preferential Hyperacuity Perimeter (Carl Zeiss Meditec) U.S. Pat. No. 6,656,131, expressly incorporated herein by reference, uses a computer and a monitor, it being possible with hyperacuity objects to detect metamorphopsia in the central and paracentral areas of the macula. This method requires relatively costly and stationary equipment.
In 1947, Marc Amsler introduced various charts for the examination of the central visual field within 10 degrees. The chart most used has a 100 mm square field, which is divided by vertical and horizontal lines that form 400 squares of 5 mm each. The lines may be black on a white background, white lines on a black background or colored lines on a white, dark or colored background. In the monocular examination, the chart is held at a distance of 30 cm from the eye, so that each square corresponds to 1 degree of the visual field. The center of the chart includes a fixation point, which the patient is to fixate constantly. In use, the patient tries to indicate whether all lines and squares can be seen, or can be seen with the same clarity, or whether there are lines which are perceived as broken, bent, wavy or twisted lines. Then, the patient tries to draw the seen changes on the chart.
See Also, (WO/2010/023470) Ophthalmic Diagnostic Apparatus, (WO/2008/020252) Ophthalmic Diagnostic Apparatus, (WO/2004/000108) Computer-Based Visual Field Testing, (WO/2003/092481) Characterization Of Visual Field Defects, (WO/2003/070089) Method And System For Assessing Eye Disease, (WO/2003/061521) Methods And Apparatus For Observing And Recording Irregularities Of The Macula And Nearby Retinal Field, (WO/2003/028534) System And Method For Full Field Oscillating Stimulus Perimeter, (WO/2002/028266) Methods Devices And Systems For Detecting Eye Disease, (WO/2002/005704) Virtual Reality Peripheral Vision Scotoma Screening, (WO/2001/072212) Computer-Based 3d Visual Field Test System And Analysis, (WO/1999/026524) Method And Apparatus For Measuring And Correcting Metamorphopsia, (WO/1998/017168) A Method Of Corneal Analysis Using A Checkered Placido Apparatus, (WO/1997/024058) Ophthalmological Self-Test Unit For Evaluating Macular Degeneration, (WO/1996/034555) Method And Apparatus For Central Visual Field Mapping And Optimization Of Image Presentation Based Upon Mapped Parameters, (WO/1996/032880) Automated Pocket-Sized Near Vision Tester, (WO/1987/004264) System And Method Of Detecting Visual Field Defects, US Application Nos. 20090273758, 20090231545, 20090143685, 20090109399, 20080309879, 20080309878, 20080137036, 20070268455, 20070200927, 20050261557, 20050122477, 20040193070, 20040125341, 20040075814, 20040046934, 20030223038, 20030212310, 20030117582, 20030081176, 20030020873, 20030002014, 20020042580, 20020024634, 20010055095, U.S. Pat. Nos. 7,771,051, 7,425,067, 7,614,746, 7,275,830, 7,220,000, 7,101,044, 6,769,770, 6,742,894, 6,736,511, 6,656,131, 6,585,376, 6,578,966, 6,494,578, 6,450,641, 6,213,605, 6,108,634, 5,892,570 5,883,692, 5,841,511, 5,838,422, 5,646,710, 5,596,379, 5,589,897, 5,880,814, 5,568,209, 5,416,540, 5,139,030, 5,121,981, 4,826,308, 4,818,091, 4,798,456, each of which is expressly incorporated herein by reference.
The clinical use of Amsler charts involves various problems:                a) Many people have difficulty in maintaining the central fixation, habitually or because of a central scotoma. When they move the fixation to other locations on the chart, then small changes in the lines of the squares are not discovered, or they are registered wrongly.        b) It is difficult for many people to mark the changes, which they see on the chart.        c) When a person has fixated a few seconds on the fixation point, then the brain begins to modulate in the visual field. The constant fixation and all the many squares and lines trigger crowding (multiple lines in the grid interfere with the perception), perceptual fading (Troxler effect where perifoveal stimuli fade or disappear), perceptual filling in (scotoma become replaced by their background and small defects in straight lines are completed) and hyperacuity (displaced lines are aligned). This means that some scotomas and metamorphopsia cannot be discovered, and that the sensitivity of the examination is reduced significantly.        
Various methods have been developed to reduce these problems of examinations with Amsler charts. The PCT application WO 87/04264 A1 (System and method of detecting visual field defects), expressly incorporated herein by reference, discloses a method using eyeglasses having a pair of cross-polarizing lenses, which may be varied selectively, so that the Amsler chart may be seen with different luminance, thus increasing the sensitivity of the examination. In the U.S. Pat. No. 5,646,710 (Ophthalmological self-test for evaluation of macular degeneration), expressly incorporated herein by reference, the Amsler chart is provided with a magnetic rear face so that it may be applied to a metallic surface, and may moreover be provided with a central fixation object consisting of a light source. The PCT application WO 99/26524 A1 (Method and apparatus for measuring and correcting metamorphopsia), expressly incorporated herein by references, uses a computer and a monitor on which an Amsler grid may be displayed. With a computer mouse, the patient is able to control a cursor and indicate the areas where parts of the grid cannot be seen (scotoma). If the patient discovers deformations of the grid (metamorphopsia), the cursor may be controlled to adjust these areas, so that all the lines in the grid become straight. All markings are stored in the computer and may be compared with subsequent examinations.
U.S. Pat. No. 6,585,376 (Test charts for metamorphopsia) expressly incorporated herein by reference, discloses a method of quantifying metamorphopsia in a horizontal and a vertical direction close to the fixation point. The method consists of different charts, where one or two fixation points, a white line or a straight row of white circular dots are printed on a black background. Metamorphopsia may be quantified by increasing the size of the dots and the distance between them.
The document US 2004/0061775 A1 discloses a digital binocular fusing apparatus where a stationary lenticular lens array produces a secondary 3D image from a primary image on a display mounted behind the lens array. The display could be a liquid crystal display or another electronic display, which are capable of producing and controlling pixels. The apparatus is designed to produce 3D images and enable visual presentation of video games and movies without using special eyeglasses or other optical apparatus adjacent the eyes of a viewer.
The document EP 0 830 839 A2 discloses a digital binocular view function inspecting apparatus for measuring the strabismus angle. A reference image for one eye and an index image for the other eye are displayed on a 3D display device. The person to be inspected can with the help of a computer mouse move the index image until the person visually recognizes the two images coincide. The computer calculates the actual amount of deviation between the two images. The document discloses that the 3D display could be a display of the parallax barrier type or of the lenticular type. The 3D display is a stationary one.
The document WO 03/092482 A1 discloses an ocular display apparatus for assessment and measuring of and for treatment of ocular disorder. The apparatus having image presentation means adapted to display a first image to one eye only of a subject, and a second, different image to the subject's other eye only so that the subject perceive a composite image including a moving object.
The apparatus is capable of presenting images to the subject on a split screen or on two separate screens. The images are perceived as 2D or 3D images. The display screens are stationary.
The document JP 2001 340300 A discloses a pupil detection device and a method of detecting the pupil position, and a 3D image display system, which use a stationary crossing lenticular system, and infrared light for detecting.